240. Search a 2D Matrix II

/**
 * @param {number[][]} matrix
 * @param {number} target
 * @return {boolean}
 */
var searchMatrix = function (matrix, target) {
  const n = matrix.length
  for (let i = 0; i < n; i++) {
    for (let j = matrix[0].length - 1; j > -1; j--) {
      if (matrix[i][j] < target) {
        break
      } else if (matrix[i][j] > target) {
        continue
      } else {
        return true
      }
    }
  }
  return false
}

var searchMatrix = function (matrix, target) {
  const m = matrix.length,
    n = matrix[0].length
  let i = 0,
    j = n - 1 // 从右上角开始
  while (i < m && j >= 0) {
    if (matrix[i][j] === target) {
      return true
    } else if (matrix[i][j] < target) {
      // 排除这行
      i++
    } else {
      //matrix[i][j] < target 排除这列
      j--
    }
  }
  return false
}